The present invention relates to a semiconductor device; and, more particularly, relates to a semiconductor device employing wires (e.g., bonding wires, for electrical connection between bonding pads of a pellet and a conductive portion for external lead-out) of aluminum or an aluminum alloy, and to techniques which are effective when applied to the bonding wire, and to the device formed by such techniques.
In the process of producing a semiconductor device, a gold (Au) wire is used as a wire which electrically connects the aluminum bonding pad of a semiconductor pellet and a base plate such as the base of a lead frame or a ceramic package. Usually, the gold wire is formed with a ball at an end thereof and then subjected to ball bonding by thermocompression.
Utilizing aluminum as the material of the wire has been considered in order to eliminate the disadvantage resulting from an increase in the cost attributed to the use of gold. Formation of a ball at an end of the aluminum wire by an electric torch or the like, whereupon a ball bonding is performed, is disclosed in Japanese Laid-Open Patent Application No. 51-140567. Thus, Japanese Laid-Open Patent Application No. 51-140567 discloses a semiconductor device wherein a ball is formed at the distal end of an aluminum wire by an electric torch or the like so as to effect ball bonding.
Although the aluminum wire is low in cost, it is inferior in its corrosion resistance. Especially when applied to the so-called resin-molded package, the wire corrodes to degrade the reliability of the device. Another problem is that the aluminum wire is lower in mechanical strength as compared with a gold wire.